The hybrid drive device is associated with the motor vehicle or forms a component part of the motor vehicle. A torque can be provided by means of a hybrid drive apparatus, which is directed to driving the motor vehicle. The hybrid drive apparatus is equipped with several drive assemblies, which are preferably configured differently. For example, the internal combustion engine is provided as a first drive assembly and the electric engine is provided as a second drive assembly. The multiple drive assemblies are preferably configured or can be operationally connected in such a way that they can jointly generate the torque directed at driving the motor vehicle at least intermittently. In this respect, it is for example possible that the torque is generated only by means of the electric engine, or only by means of the internal combustion engine, or with the electric engine as well as with the internal combustion machine.
Several operating means are supplied at least intermittently to the internal combustion machine in order to operate it, in particular the fuel and the lubricant. The fuel ultimately serves to provide the torque moment with the internal combustion engine, while the lubricant is used for lubrication of the internal combustion engine. The fuel is combusted in the internal combustion engine and consumed in this manner. The lubricant, on the other hand, is provided in a lubricant circuit, wherein the internal combustion engine supplies the lubricant for example from a lubricant reserve so that it is applied to the lubrication of the internal combustion engine and after that, the lubricant or at least the remaining lubricant is temporarily stored again in the lubricant reserve. The lubricant reserve is for example provided in a lubricant tank of the hybrid drive apparatus of the motor vehicle.
Under certain circumstances or in certain operating states of the hybrid drive apparatus or of the internal combustion engine, introduction of fuel into the lubricant can occur, in particular during a warm-up operation of the internal combustion engine. The warm-up operation is present as long as the temperature of the internal combustion engine is lower than its operating temperature, wherein the latter is achieved within the context of a quasi-stationary operation of the internal combustion engine. The warm-up operation of the internal combustion engine is carried out during an operation of the internal combustion engine at a temperature that is lower than the operating temperature. When the temperature of the operating temperature is reached, the warm-up operation of the internal combustion engine is switched to a normal operation of the internal combustion engine. The warm-up operation differs from the normal operation for example in that a different operating strategy is used, in particular because the internal combustion engine is operated in the warm-up operation with a lower efficiency than during the normal operation in order to generate heat which serves to warm up the internal combustion engine.
When fuel is introduced into the lubricant, the latter is diluted so that the now diluted lubricant can no longer provide its lubricating function to the extent intended.
The introduction of the fuel into the lubricant occurs to a larger extent within the context of the hybrid drive apparatus in comparison to conventional drive apparatuses because the motor vehicle can be partially operated solely by the means of the electric engine, which means that the internal combustion engine is at a standstill and therefore must be started more frequently during the travel of the motor vehicle. This means, in view of the preceding explanations, that the warm-up operation of the internal combustion engine during which fuel can be introduced into the lubricant is conducted more frequently, so that the dilution of the lubricant is intensified.
From document DE 10 2013 216 215 A1 is known for example a method for a motor in a hybrid motor vehicle, wherein a motor is operated in reaction to the fact that the oil dilution is higher than a threshold value in order to increase the motor temperature for a period of time above a threshold temperature. The duration of the time period is based on the difference between the oil dilution and the threshold value so that the duration of the time period is increased when this difference is increased.